The invention concerns an apparatus for thermo-mechanical decoupling of the housing and stationary part of a dynamo-electric rotating machine, an application of this apparatus and an appropriate rotating machine.
The invention relates to rotating machines where a stationary part (stator or stator core) is to be supported in a casing, and thus, it concerns any kind of motor or generator. The rotating part, also referred to as rotor, is arranged within the stator.
This connection between the stator core and the housing shell is particularly advantageous when the differences in temperature and radial stiffness of the casing and the stator core are high.
This is particularly true of bulb turbine generators, where the housing is cooled by the passing water, which is normally cool, but where the stator core heats up during operation. In addition, the water pressure acting on the housing shell exerts a radial load on the housing and stator core. Both the temperature difference and the possible water pressure result in tangential compressive strains in the stator core that can lead to mechanical instability of the stator core. This may result in the bulging of the sheets or sheet layers of the stator core. Heavy bulging may damage the sheets, the winding and other parts of the generator.
Basically, there is a state of the art showing a non-rigid stator position, which goes far back in time. A dynamo-electric machine is known from GB 800613, which has internal frame rings that are connected to the stator core frame rings via spring-type devices. The finish of these spring-type devices is not disclosed. However, using just any type of spring-like devices will not ensure that the stator core position is sufficiently secure in axial direction and that the centered alignment is maintained.
Pamphlet DE 2852391 A1 discloses a stator casing with two hollow cylinders which are thermally insulated against each other. Due to this insulation, the inner hollow cylinder has approximately the same temperature as the stator core and thus the temperature-related compressive strains are minimized. The inner hollow cylinder must, however, have a very solid design because it is attached only at its ends and must take up all forces.
Pamphlet JP 56107767 A discloses a stator consisting of two cylinders which are connected to each other via axially mounted ribs that are arranged in a triangle. The stator core ledges are fixed to the cylinder between the inner vertexes of the triangles, in order to achieve higher radial flexibility.